Polyurethanes based on polybutadiene soft segments with a functionality of 2.0 are disclosed in Yokelson. et al. (U.S. Pat. No. 5,589,543). Yokelson. et al., however, does not disclose the use of polyurethanes as thermoplastics. Commercial hydroxy terminated polybutadienes are used to formulate various polyurethane casting resins and binders. However, since these polybutadienes have functionalities greater than 2.0, they form thermoset polyurethane materials. Polyurethanes based on these polybutadienes cannot be processed as thermoplastics (extrusion or injection molding processes). Hydroxy-terminated polybutadienes having a functionality of 2.0 are disclosed in Chung. et al. (U.S. Pat. No. 5,247,023), Grubbs. et al. (U.S. Pat. No. 5,750,815) and Nubel. et al. (U.S. Pat. Nos. 5,512,635, 5,559,190, 5,519,101 and 5,403,904). However, these polybutadienes, have not been used to make a thermoplastic polyurethane material.
Polyurethane elastomers made from polybutadiene diols having a functionality of 2 are disclosed as being manufactured by making a toluene diisocyanate (TDI) prepolymer of the polybutadiene diol, blending in methylene bis-ortho chloroaridine (MbOCA) then curing the mixture by compressing it under elevated temperature and pressure. Additionally, such elastomers are disclosed as being made from a one-shot procedure, by blending 1,4-butanediol with the polybutadiene diol, adding molten diphenyl-methyl diisocyanate (MDI) and compressing the reaction mixture under elevated temperature and pressure, Frisch. et al., Cell Polym 1996, 15(6), 395. However, it has been found that polyurethanes cast from mixtures of MDI, a polybutadiene diol, and 1,4 butanediol, by the prepolymer process have very poor initial mechanical properties. Even after extended post-cure at elevated temperature (18 h, 110.degree. C.), the polymers are not sufficiently tough to be cut and tested for mechanical properties. However, we have surprisingly found that extruding the cast materials leads to marked improvement in their mechanical properties.